Mario Manningham tore two knee ligaments on this play against the Seahawks. / Joe Nicholson, USA TODAY Sports

by Mike Garafolo, USA TODAY Sports

by Mike Garafolo, USA TODAY Sports

The diagnosis for Mario Manningham was as bad as it looked on replay Sunday night.

The San Francisco 49ers wide receiver tore the ACL and PCL in his left knee during the team's blowout loss to the Seattle Seahawks, according to a person informed of the results of tests conducted on Manningham Monday. The person spoke to USA TODAY Sports on condition of anonymity because the team hasn't announced the full extent of the injury yet.

Manningham signed a two-year, $7.5 million deal with San Francisco this spring after capping his four seasons with the New York Giants with a 38-yard catch up the left sideline to spark the game-winning drive in Super Bowl XLVI.

Manningham had 42 catches for 449 yards and one touchdown in his first season with the Niners.

It's the third season-ending injury to a key player for the 49ers this month. The team also lost running back Kendall Hunter to a torn Achilles tendon. Wide receiver and returner Kyle Williams tore his ACL.

There was also the suspension of running back Brandon Jacobs for conduct detrimental to the team. Jacobs is suspended for one more game and will likely be released before the postseason begins.